Multi-display systems for displaying a plurality of windows (a multi-window) of a plurality of different applications (a multi-application) on a plurality of displays have conventionally been known. For example, Patent Document 1 discloses a system that displays a window for displaying, on a built-in monitor, details displayed on an external monitor upon detection of disconnection of the external monitor during use of an extended desktop function, which enables prevention of a non-operable state.